I have a small Damson plum with about 50 small green plums just 7 feet away from a med sized golden delicious apple. Just finished bagging the apples and noticed P. curc damage on about 20% of the small green apples (dime size) - but no damage on the plums (also dime size). Anecdotal - yes, but I'm sure there is no rule.
I even got 2 of the little brown beasts with their ovipositors imbedded in the friut. Requiem mass was at 8 pm last night.
Last year, I used my fingernail (as per a NAFEXer suggestion) to extricate the PC ovum. The developing apple had a small scar, but otherwise was still quite edible. I realize this is not an option for commercial endeavours.
I have a Clapps pear and, for the 1st time, would have had a reasonable crop. About 1/3rd of the quarter sized pears simply turned black. They were ravaged from the inside by small white worms, (WEB enquiries indicated apple maggots?). I did spray at petal fall.
I also noticed for the 1st time, that some of my apple leaves exhibited what looks like peach leaf curl. Could this be a ramification of not having applied a dormant spray? (too much rain when I had the time)
I am also assuming the haphazard weather in Jan (very warm), cold Feb, and overly wet spring has caused sporadic apple development in some trees. A couple of trees are loaded, whereas some that I expected to thin have almost no fruit. Genetic diversity?